Metal organic framework-derived Co3O4/NiCo2O4 hollow double-shell polyhedrons for effective photocatalytic hydrogen generation

Hollow polyhedron materials have the characteristics of low density, high area ratio, strong light absorption and the short distance of mass transport, etc., which have come to the foreground in recent years. In this work, ZIF-67/Co-Ni double hydroxide (DH) was prepared using ZIF-67 as a precursor and then calcined to form Co3O4/NiCo2O4 hollow double-shell polyhedrons (HDSPs). This unique self-supporting hollow double-shell catalyst effectively avoids the aggregation of the catalyst and provides a unique reaction platform for the photocatalytic hydrogen production reaction. On the one hand, the thin shell reduces the penetration loss of incident light, and there are multiple refractions and scattering occur inside the shell, thereby effectively improving the light-trapping ability. On the other hand, the Co3O4/NiCo2O4 HDSPs not only shortens the transport distance of photo-generated carriers but also provides abundant active sites, which effectively inhibiting the recombination of electrons and holes. Density functional theory (DFT) calculations show that the formation of a NiCo2O4 shell outside of Co3O4 is more conducive to the separation and transfer of electrons. Therefore, the Co3O4/NiCo2O4 HDSPs can facilitate the separation and migration of carriers and effectively increase the hydrogen evolution rate of the catalyst. This work shows the important role of hollow double-shell materials and provides new ideas for the preparation of hollow double-shell catalysts.